In the handling of containers preparatory to filling them, whether it is a beverage or food stuffs, it is necessary to inspect the containers for foreign matter and to be sure nothing is inside that would allow contamination of the contents. Apparatus for inspecting the interior of containers includes those which have probes to enter the container, and those which inspect from the outside with the aid of light or radiant energy.
Current systems for handling containers of the above classes require inspection means capable of performing the interior inspection while the containers are in motion of the order of up to 800 containers per minute passing the inspection station. This fast acting capability eliminates the types of inspection devices which require each container to stop during the inspection interval, though rotation in the stopped position may be carried out. The latter types of inspection apparatus include those disclosed in Mathias U.S. Pat. No. 3,267,796 of Aug. 23, 1966; Mathias U.S. Pat. No. 3,355,980 of Dec. 5, 1967; Sorbie U.S. Pat. No. 3,327,849 of June 27, 1967; Kidwell U.S. Pat. No. 3,479,514 of Nov. 18, 1969; and Bentley U.S. Pat. No. 2,943,531 of July 5, 1960.
The background patents pertaining to the general arrangement of apparatus for inspecting containers while in movement is exemplified in Wyman U.S. Pat. No. 3,191,773 of June 29, 1965; Gulliksen U.S. Pat. No. 2,265,037 of Dec. 2, 1941; Gender et al U.S. Pat. No. 3,631,255 of Dec. 28, 1971; Babunovic et al U.S. Pat. No. 3,629,595 of Dec. 21, 1971; Stogoff U.S. Pat. No. 1,926,824 of Sept. 12, 1933; Calhoun et al U.S. Pat. No. 3,349,906 of Oct. 31, 1967; and British Pat. No. 905,729 of Sept. 12, 1962.
In addition to the foregoing background disclosures, prismatic devices for various uses have been disclosed in light transmitting cases in such nonanalagous background art as Gould U.S. Pat. No. 2,231,186 of Feb. 11, 1941; Scott U.S. Pat. No. 2,513,367 of July 4, 1950; and Miller U.S. Pat. No. 2,939,962 of June 7, 1960. The general type of prism device employed in the present invention has been disclosed in a military standards handbook for optical design No. MIL-HDBK-141 dated Oct. 5, 1962, at page 13-37 where a typical reversion prism has been shown in FIG. 13.55. This prism may also be designated as a "K" prism.
In the case of each of the disclosures covered by the above enumerated patents and the publication, the prism devices leave a great deal to be desired in the inability to perform the necessary inspection of the complete bottom and lower side walls of containers, and as a result a resort has been directed toward the use of such inspection apparatus as that disclosed by Richardson U.S. Pat. No. 2,798,605 of July 9, 1957, wherein a plurality of container side video inspecting devices, not only look into the containers but also look at the side wall thereof.